This invention relates to laser output controlling devices, and more particularly to a laser output controlling device which controls a laser output on the parameters of gas pressure and current by a simple operation.
In a laser knife or a laser machining device, the laser output must be controlled. In the laser output control, for instance in the case of a CO.sub.2 laser, a discharge current value must be controlled, and the gas pressure in a laser oscillating tube should also be controlled since the CO.sub.2 laser output varies with discharge current and gas pressure. More specifically, when the discharge current is 10 mA, the CO.sub.2 laser output is about 8.5 W with a gas pressure 15 Torr, about 13 W with a gas pressure 20 Torr, about 17 W with a gas pressure 25 Torr, and about 20 W with a gas pressure 30 Torr, as indicated in FIG. 1. When the gas pressure is set to 20 Torr, the laser output is about 21.5 W with a current 20 mA, and is about 25.5 W with a current 30 mA.
Heretofore, the gas pressure and the current value have been adjusted individually. That is, the gas pressure has been controlled by adjusting the control value of the gas pipe, while the current value has been controlled with a control knob.
In such a conventional device, the gas pressure and the current value are controlled manually, and simultaneous control of the two parameters is considerably difficult. If a person unskilled in the control of the device attempts to control the parameters, he may cause serious trouble. For instance, when it is desired to obtain a laser output 25 W in FIG. 1, the current value can be set to 13 mA with a gas pressure 30 Torr, but the laser output is greatly changed with a slight change in current. Further, when it is desired to obtain a laser output 30 W, the gas pressure can be set at 22 Torr with a current 30 mA, but the laser output will changed greatly with a slight change in gas pressure.
The controls for these two parameters cannot be easily controlled by a person who may have a laser attachment in hand, and therefore a doctor performing an operation with a laser knife cannot freely control the gas pressure and the current value. Thus, the conventional device is unsatisfactory from both safety and reliability viewpoints.
There is a device known in the art in which the gas pressure is fixed so that only the current value is controlled. However, since the characteristic curve has a considerably steep part and the output peak is limited, as shown in FIG. 1, it is difficult to provide a laser output which is stable over a wide range.